Many different overhead industrial light fixtures exist to serve needs such as factory and warehouse illumination and the like, and a number of advances have been made over the years. Among significant advances in industrial light fixtures are the fixtures disclosed in U.S. Pat. No. 6,601,975 (Overhead Industrial Light Fixture With Two-Piece Housing); U.S. Pat. No. 6,394,869 (Method for Manufacture of Overhead Industrial Light Fixture); and U.S. Pat. No. 6,467,927 (Overhead Industrial Light Fixture With Mounted Reflector), all of Ruud Lighting, Inc. Such fixtures provide significant advantages, including compactness, simplicity of manufacture, ease of installation and service, pleasing appearance, and other advantages set forth in the disclosures.
Despite these and other such advances in the field there remains a need for further improvement in industrial light fixtures, preferably without compromising the advantages previously provided including those related to ease of manufacture, storage, shipment, installation, etc.
Overheating is a common problem for industrial light fixtures, and among the overheating problems with certain devices of the prior art is a problem of inadequate heat dissipation away from power-related components such as ballasts, lamps and lamp sockets. Certain components, particularly capacitors, are limited in their ability to tolerate high temperatures. It is critical to the life of certain components, mainly those that are particularly heat-sensitive, that steps be taken to prevent costly damage or, worse, a premature end of the life of the fixture. Overheating can damage power-related components which compromises the longevity of the light fixture and its components. Minimal gains in temperature reduction yield very substantial gains in component life and, therefore, in overall fixture longevity.
While the concern of overheating has in some cases been addressed by use of cooling fans, such fans are often loud and contrary to the highly desirable goals of fixture compactness, low cost, and operational reliability. Similarly, use of barriers and other insulating features have disadvantages as they increase manufacturing costs and also defeat the goal of compactness and ease of service. Plastic ballast enclosures may be used to thermally isolate the ballast; however, such enclosures are contrary to heat removal and can exacerbate problems.
In some cases, thermal protection devices to break circuits upon overheating are utilized. However, under certain conditions such devices may fail to perform properly, thereby allowing a lighting fixture to overheat and possibly lead to combustion. Such thermal protection devices also add cost.
Another possible approach to dealing with certain of the above problems and shortcomings is use of a housing with one or more external power-related components, such as the ballast. However, this approach complicates installation, increases cost, makes achieving a pleasing appearance difficult at best, and is directly contrary to the goal of compactness.
Another problem is that certain structures of the prior art may not be particularly well-adapted to suppress and/or contain any combustion that might occur. In certain cases, the nature of the ballast (including manufacturing defects or minimal defects that may occur from handling or the like) or improper electrical characteristics or conditions can lead to ballast failures and shorts which in turn lead to combustion of materials (e.g., organic insulation materials). As can be seen, the goals of achieving cooling and suppressing oxidation in an overhead industrial light fixture tend to be at odds with each other. Accomplishing one of these critical goals tends to lead to loss of the other. The benefits realized in being able to accomplish these two goals in one fixture would be significant.
For one thing, facilitating cooling of the industrial light fixture tends to keep the components cool thereby enhancing the life of the components and the entire fixture and preserving overall quality. And, substantially reducing the inflow and outflow of combustion-supporting air in critical portions of an overhead industrial light fixture would tend to suppress and limit any combustion which might occur, and thus reduce dangers typically associated with product failures. If these critical advantages could be combined in an overhead lighting fixture, the resulting fixture would have improved quality, endurance and longevity.
Accordingly, there remains in the art a need to provide an overhead industrial light fixture that more effectively removes heat from the housing, without sacrificing other advantages of benefits realized from earlier development work.